Fold a 2-bit shift into decodeSpectrum(), saves 1MHz on ARM, +2%

speedup.


git-svn-id: svn://svn.rockbox.org/rockbox/trunk@24660 a1c6a512-1295-4272-9138-f99709370657

1 files changed, 8 insertions, 12 deletions

diff --git a/apps/codecs/libatrac/atrac3.c b/apps/codecs/libatrac/atrac3.c
index 467f42f161..157aff57f7 100644
--- a/apps/codecs/libatrac/atrac3.c
+++ b/apps/codecs/libatrac/atrac3.c
@@ -410,13 +410,19 @@ static int decodeSpectrum (GetBitContext *gb, int32_t *pOut)
             SF = fixmul31(SFTable_fixed[SF_idxs[cnt]], iMaxQuant_fix[subband_vlc_index[cnt]]);
 
             /* Inverse quantize the coefficients. */
+
+            /* Remark: Hardcoded hack to add 2 bits (empty) fract part to internal sample
+             * representation. Needed for higher accuracy in internal calculations as
+             * well as for DSP configuration. See also: ../atrac3_rm.c, DSP_SET_SAMPLE_DEPTH 
+             * Todo: Check spectral requantisation for using and outputting samples with 
+             * fract part. */
             if((first/256) &1) {
                 /* Odd band - Reverse coefficients */
                 for (pIn=mantissas ; last>first; last--, pIn++)
-                    pOut[last] = fixmul16(*pIn, SF);
+                    pOut[last] = fixmul16(*pIn, SF) << 2;
             } else {
                  for (pIn=mantissas ; first<last; first++, pIn++)
-                    pOut[first] = fixmul16(*pIn, SF);
+                    pOut[first] = fixmul16(*pIn, SF) << 2;
             }
 
         } else {
@@ -777,16 +783,6 @@ static int decodeChannelSoundUnit (GetBitContext *gb, channel_unit *pSnd, int32_
     numBands = (subbandTab[numSubbands] - 1) >> 8;
     if (lastTonal >= 0)
         numBands = FFMAX((lastTonal + 256) >> 8, numBands);
-        
-    /* Remark: Hardcoded hack to add 2 bits (empty) fract part to internal sample
-     * representation. Needed for higher accuracy in internal calculations as
-     * well as for DSP configuration. See also: ../atrac3_rm.c, DSP_SET_SAMPLE_DEPTH 
-     * Todo: Check spectral requantisation for using and outputting samples with 
-     * fract part. */
-    int32_t i;
-    for (i=0; i<1024; ++i) {
-        pSnd->spectrum[i] <<= 2;
-    }
 
     /* Reconstruct time domain samples. */
     for (band=0; band<4; band++) {